































































































































































































































































































































fH~t> 


i 


THE GLUE BOOK 



















MODERN GLUE-TESTING LABORATORY 


(Courtesy of A. T. Deinzer, Monroe, Mich.) 








THE GLUE 
BOOK 


HOW TO SELECT 
PREPARE AND 
USE GLUE 

A SHORT, PRACTICAL 
DISCUSSION OF MATTERS 
IMPORTANT TO EVERY 
GLUE USER 


J. A. TAGGART, TOLEDO, 0. 









COPYRIGHT 1913, J. A. TAGGART 





AUTHOR’S NOTE 


T HE purpose of this manual is to 
provide a practical guide for glue 
users, to help in eliminating waste 
and improving the quality of product. 

That there is an enormous waste due 
to improper preparation and use of glue 
is well known to all who are in touch 
with the subject. 

Some authorities estimate that 70% 
of the glue used in the United States is 
improperly handled. The actual waste 
is said to be in excess of 25% of the 
amount of glue used; to say nothing of 
the loss due to imperfect condition of the 
completed work. 

The writer knows from actual experi¬ 
ence that many glue users are ignorant 
of the proper methods to be employed; 
and that many others are careless, or 
indifferent. 


7 





THE GLUE BOOK 


The handling of glue is a subject on 
which much new light has been shed in 
recent years. There is no longer any 
reason why the glue user should not 
know the correct methods to follow. 

This treatise is intended as a handbook 
for the glue user who is interested in 
increasing the efficiency of his operations. 

Technical expressions have been 
avoided, the whole matter being set forth 
as much as possible in the everyday terms 
in familiar use in the glue-room. 

So far as the author can learn, from 
an extended investigation, no book has 
been published on this subject exactly 
answering the needs of the average glue 
user. Several excellent works are avail¬ 
able which would be interesting to a man 
technically trained in the subject; but 
although they embody many helpful 
suggestions, they are not in such form 
8 





THE GLUE BOOK 

as to be of the greatest value to the prac¬ 
tical man. No pretense is made for the 
present manual of disclosing new facts; 
but rather of assembling in handy and easy 
reference form a summary of the best 
modern practice which the glue user of 
today may rely upon as a safe and con¬ 
venient guide. 


9 









THE GLUE BOOK 

TABLE OF CONTENTS 

CHAPTER I 

IMPORTANCE OF THE INDUSTRY 

Glue industry founded in America by Peter 
Cooper — increase in capital invested — 
increase in production — variety of uses 
—increase in requirements.Page 15 

CHAPTER II 

THE MANUFACTURE OF GLUE 

Sources from which glue is made — boiling 
the stock — drying — preparation in com¬ 
mercial form.Page 17 

CHAPTER III 

TESTING AND GRADING GLUE 

Grades established by Peter Cooper—the tests 
—viscosity or fluidity test — the jelly test— 
apparatus for making jelly test — the finger 
test—a simple, practical test for glue users— 
sampling — bubbles — surface indications — 
color indications — alkaline or acid quality— 
breaking quality — foam — grease — keeping 
properties—odor—laboratory test.. .Page 25 

CHAPTER IV 

CORRECT METHODS IN THE GLUE ROOM 

Much waste through faulty methods — 
importance of correct practice — soak glue 
in cold water before melting — test glue by 
ll 







THE GLUE BOOK 


water absorption — appliance for water ab¬ 
sorption test— melting or dissolving glue — 
do not heat higher than 150° F. — apply 
heat indirectly — live steam ruins glue — use 
thermometer — heat glue slowly — cleaning 
the melting pot — importance of using cop¬ 
per, brass or aluminum utensils — guard 
against evaporation — melt only the amount 
required — importance of cleanliness — keep¬ 
ing the glue room warm — use by weight — 
storing — applying glue — securing workers' 
co-operation.Page 43 


CHAPTER V 

MODERN GLUE ROOM EQUIPMENT 

Modern appliances now available for all users 

— only copper, brass or aluminum should 
come in contact with glue—the scientific glue 
heater—the automatic temperature controller 

— keep steam away from glue — glue spread¬ 

ers— clamps and presses — distributing glue 
in large plants.Page 65 

CHAPTER VI 

WHICH GLUE TO USE 

Accurate records important — the best glue 
for wood joints — veneers — sizing — paper 
boxes — belting and other leather goods — 
bookbinding — emery purposes — how much 
to pay — waterproof glue—vegetable glue — 
quick setting glue—flexible glue Page 79 


12 








THE GLUE BOOK 








CHAPTER I 


IMPORTANCE OF THE INDUSTRY 


G LUE is now so extensively used, 
and for so many different pur¬ 
poses, that it certainly deserves 
much more intelligent treatment 
at the hands of users than it has received 
heretofore. 

Since 1837, in which year Peter Cooper, 
who may justly be regarded as the founder 
of the glue-making industry in the United 
States, produced the first American-made 
glue, the yearly output has steadily 
increased. 

By 1880, the amount of capital in¬ 
vested in the making of glue had reached 
$4,000,000. In 1905, it was $10,000,000, 
and is now between $12,000,000 and 
$13,000,000. 

The annual production has increased 
in about the same ratio. In 1880, it 
was $4,000,000; at present it is about 
$15,000,000. 


15 






THE GLUE BOOK 


Glue is an important by-product of the 
great packing houses. Those in touch 
with the industry know how extensively 
glue enters into the manufacture of 
articles of everyday use. The general 
public hardly realizes that glue is used not 
only in making wood-joints and veneers, 
but in the production of paper, of silks, 
hats, carpets, rugs, and hundreds of other 
necessities. 

America now produces glue of excellent 
quality to meet practically all require¬ 
ments. So great are the requirements 
that almost the entire amount of the 
American-made glue is absorbed by the 
home demand. 


16 





CHAPTER II 

THE MANUFACTURE OF GLUE 

A N understanding of the sources 
from which glue is derived and 
of the processes of manufacture 
will be found of practical impor¬ 
tance to the glue user. It will give many 
valuable side-lights on the proper meth¬ 
ods of preparation and handling. 

Glue is an organic substance of adhe¬ 
sive properties obtained from the hides, 
skins, bones and sinews of cattle, sheep, 
deer, horses, and other animals. Tails, 
snouts, ears, and the pith of the horn are 
also used. Some glue is produced from 
the heads, bones and sinews of fish. 

The tendons and intestines of many 
animals, the swimming bladder of many 
varieties of fish; rabbit skins, or “coney,” 
from which the fur has been removed; old 
waste leather, such as gloves, butchers' 
offal, or “country bone;” “junk” bones, 
and much other apparently worthless 
matter, all contribute to the raw material 

17 






THE GLUE BOOK 


of the glue-maker. In its broadest sense 
glue may be understood to include gela¬ 
tine, but the use of the word is here con¬ 
fined to the substance known commer¬ 
cially as glue, and which in contrast with 
gelatine has greater adhesiveness, stiff¬ 
ness, and elasticity, and is also darker 
in color and more nearly opaque. 

Neither gelatine nor glue exists already 
formed in nature; they are both the 
products of the action of heat and water 
on nitrogenous animal tissue. It is not 
definitely known just how this change 
takes place. Some writers regard glue 
as impure gelatine; others believe that 
there is a difference in nature between 
gelatine and glue. This question is with¬ 
out present importance for our purpose. 

BOILING THE STOCK 

Glue is produced by boiling the animal 
substances mentioned above, and drying 
the resulting liquor. 


18 





THE GLUE BOOK 


The following may be noted in con¬ 
nection with the use of skins. The outer 
covering, in which the wool, fur or hair 
is rooted, is of no importance to the glue- 
maker. The portion that produces the 
glue lies next to it, being composed of 
fibres which run in every direction and 
contain the fluid matter which aids in 
keeping the skin moist and pliable. The 
fat cells are directly beneath the glue- 
yielding portion, and as fat is undesirable, 
because it makes the glue greasy, the 
shreds of fat are saponified by being sub¬ 
jected to a lime bath. The lime bath is 
also useful in removing any hair still 
adhering; and is used also in preparing 
tissue, to remove bloody and fleshy 
particles. 

This part of the process may consume 
from one to three days. 

It may be noted in passing that the 
older the animal, the more solid the glue 
will be. On this account many manu¬ 
facturers sort the skins before using. 

19 





THE GLUE BOOK 


Being animal stock, the raw material 
of glue is subject to decomposition, and 
the scraps of hide are therefore carefully 
preserved, especially diu-ing the summer 
season. 

The tanneries supply most of the hide 
stock, but only waste pieces reach the 
glue manufacturer, as leather is more 
valuable than glue, and the larger por¬ 
tion is therefore reserved for the tan¬ 
ner’s use. Various names are used to 
describe the parts of hide that the tanner 
discards for the glue-maker’s use — the 
heavy trimmings are “pieces;” the hide 
pared off the hair or grain side, “skivings;” 
the parts scraped from the flesh side are 
“fleshings.” 

At the packing houses the heads, feet, 
ribs, and other bony structures go direct 
to the glue-room. If bone is sweet and 
fresh it is known as “green,” or “packer” 
bone. The waste of button and knife 
factories is also used. 


20 





THE GLUE BOOK 


Bones are usually ground, and they are 
treated with a sulphuric acid bath to 
attack and separate the lime and gelatine 
of which the bone is composed. Bones, 
after being treated in this way, become 
pliable and soft, and the sulphuric acid 
is then removed by centrifugal force. 

The acid must all be removed, as the 
glue will granulate if any remains. 

Other parts of the stock are always 
carefully washed before boiling. 

After the stock has been prepared, it 
is placed in a boiler with false bottom 
provided with an opening through which 
the liquid may be run off. The boiling 
of the stock is an operation that must be 
carefully conducted, as the application 
of a greater degree of heat, or for a longer 
time than is necessary, damages the glue. 

The boiler is heated by direct firing. 
As the boiling proceeds, test quantities 
of the liquid are run off for examination, 
and when a sample is found on cooling 
to form a stiff jelly, it is ready to draw off. 

21 





THE GLUE BOOK 


The first boiling usually occupies about 
eight hours. When the liquid has been 
run off from this boiling, more water is 
added and the boiling is continued. This 
operation is repeated until the stock has 
yielded all of its gelatinous matter. As 
many as six or eight boilings may be made. 

The liquid first run off — the “first 
boiling'' —is always best, as the effect 
of repeated or prolonged application of 
heat is to weaken the glue tissue. The 
later boilings are also as a rule darker in 
color than the earlier ones. 

DRYING 

The glue solution from the boiling 
process is run into wooden troughs or 
“coolers," about 6 feet long, 2 feet broad, 
and a foot deep, in which the solution 
sets in a firm jelly. 

When set, a little water is run over the 
surface, the jelly is detached from the 
cooler, cut into uniform slices of the 
thickness desired, and placed on galvan¬ 
ized or linen nets to dry. 

22 





THE GLUE BOOK 


Drying may be done in the open air 
if weather conditions are favorable, or in 
a drying-room. The latter method is 
preferable. Conditions can be regulated 
to insure uniform drying. 

Piles of the nets, or “stacks,” are loaded 
on trucks and taken into the drying- 
room, where they are exposed to the 
effect of warm air currents induced by 
blower or pressure fans, or exhaust or 
suction fans. 

The drying is a source of concern to the 
manufacturer. It is extremely important 
to keep the temperature at just the right 
point, to protect the glue from dust and 
dirt, and to avoid the possibility of bac¬ 
terial growth in the glue jelly, which is 
very susceptible to the development of 
harmful organisms. 

The final form of the glue will be in 
sheets, strips or flakes, or ground. For 
commercial purposes it is put up in pack¬ 
ages, bags and barrels. 


23 













CHAPTER III 

TESTING AND GRADING GLUE 

T HERE is as yet no uniformity of 
opinion among glue manufacturers 
and glue users as to how glue 
should be tested and graded. In 
a general way the manufacturer knows 
what kind of glue a certain stock will 
produce; but on account of variations 
that are sure to occur, it is necessary to 
subject each glue to certain tests, accord¬ 
ing to standards more or less definitely 
established. 

The grades in general use are those 
originally employed by Peter Cooper, 
and are as follows: 

A EXTRA 
No. 1 
1 x 

ik, m ij4 m in, i 7 a 


The only way to determine which is 
the best glue to use, is by trying out 
various grades in actual practice. The 

25 








THE GLUE BOOK 


best glues for ordinary uses are well 
understood (see pages 79 to 85 for sugges¬ 
tions on this subject). Between two or 
more glues of any one type, actual experi¬ 
ment is the only safe guide. Most glue 
men will give you good advice; but above 
all, keep accurate records of results of the 
different grades used. When you have 
found the right glue, keep to it. 

THE TESTS 

Glue is graded on physical character¬ 
istics rather than on chemical composi¬ 
tion. Various chemical tests have been 
proposed, but they are unimportant so 
far as practical working value is con¬ 
cerned. 

The most important physical tests are 
those for viscosity, and jelly strength. 

VISCOSITY OR FLUIDITY TEST 

The test for viscosity, or fluidity, is 
based on the idea that the greater the 
tenacity of the glue, the greater will be 
26 





THE GLUE BOOK 


its cohesiveness, and the less will be its 
flowing power. In other words, the 
higher will be its viscosity. 

In testing for viscosity, water is used 
as a standard. A solution is made of the 
glue, and the rate of flow of the solution 
at a certain temperature is compared 
with the rate of flow of water under the 
same conditions. 

Several devices are on the market 
under the name of “viscosimeter” for 
measuring the viscosity of glue. 

While they vary in detail they are in 
principle a pipette from which the glue- 
solution flows at a given temperature. 
The time required for the glue to run out 
of the pipette as compared with the time 
consumed in the same operation by the 
same quantity of water gives the relative 
viscosity of the glue. 

The viscosity test is not entirely accur¬ 
ate in itself, but taken in connection with 
the jelly test it forms a very satisfactory 
basis for grading. 


27 





THE GLUE BOOK 


THE JELLY TEST 

The jelly test is based on the compara¬ 
tive resistance power of the various glue 
jellies. Several mechanical devices for 
determining jelly-strength have been per¬ 
fected. One of these consists of a brass 
vessel which rests upon the glue jelly, 
and into which shot is poured; the weight 
of the cup and the contained shot upon 
having penetrated to a certain depth in 
the glue jelly, gives a figure which 
expresses the comparative strength of 
the jelly with the standard. 

APPARATUS FOR MAKING JELLY TEST 

Another apparatus that has been found 
accurate and practical is the device illus¬ 
trated on the next page. It consists of a 
pressure tube (A), over the mouth of 
which is stretched a thin rubber dia¬ 
phragm (B). The tube connects to a rub¬ 
ber bulb (M) and to a pressure gauge, or 
manometer (E) with a scale (F). The 
pressure tube is filled with water to the 
28 













































THE GLUE BOOK 


point (C). The manometer tubes also 
contain water. A three-way stop-cock 
(D) connects the tubes either to the 
bulb (M), or to the air, depending on the 
position. Below the pressure tube is a 
brass table (G), on which is placed the 
glass containing the glue jelly to be tested. 

When the glass is in position, the table 
is raised by means of a threaded wheel 
until the glue surface forces the water 
resting on the flexible diaphragm up to 
the fixed mark L. Then the stop-cock 
is turned to connect the pressure tube 
and gauge to the rubber bulb. By press¬ 
ing the bulb the water is forced down in 
the pressure tube and so expands the 
diaphragm into the jelly, the liquid in 
the gauge rising simultaneously. Pres¬ 
sure on the bulb is continued until the 
water reaches the mark N. 

Thereupon the stop-cock is again 
turned, the water is held at the point N, 
and the pressure is indicated by the 
height of the liquid in the gauge. The 

30 





THE GLUE BOOK 


degree of pressure is the measure of the 
consistency of the glue jelly. 

The initial contact between the jelly 
and the rubber diaphragm is always the 
same, all jellies therefore having the 
same initial pressure. When the dia¬ 
phragm is forced down into the jelly, 
the pressure required depends entirely 
upon the resistance that the jelly offers. 
The slightest difference in the consist¬ 
encies of the various jellies will alter the 
pressure required, the differences being 
accurately recorded by the gauge upon 
the scale. 

Advantages of this apparatus are that 
the relative value of the jelly compared 
with the standard is expressed in con¬ 
crete figures; the method of operation is 
simple; and the instrument is so sensitive 
that it will record a change in reading 
between two samples of glue in which a 
difference of rfoth ounce of dry glue is 
used. Repeated tests may be made on 
the same jelly, as the surface is not 

31 





THE GLUE BOOK 


broken. With a little practice a single 
glue may be tested in twenty seconds, 
or less. 


THE FINGER TEST 

One of the most satisfactory methods 
of determining jelly-strength — and the 
one perhaps in most general use, is the 
finger test. 

In this test the various glue jellies are 
arranged before the tester, who presses 
each with the tip of the finger, comparing 
it with the standard as to resistance- 
power. While this may seem to expose 
the final decision too greatly to the per¬ 
sonal equation, as represented by the 
personality of the glue-tester, it is never¬ 
theless true that an expert develops the 
most extraordinary precision, arriving 
at conclusions that are corroborated by 
the results of other tests and by the 
results in actual practice. The work of 
the glue-tester is analogous to that of the 
coffee-taster and the tea-taster, or experts 

32 





THE GLUE BOOK 


in other lines, who through a highly 
developed and keenly discriminating 
sense of taste, or touch, or smell, deter¬ 
mine with extreme nicety the physical 
characteristics of the substances that 
they are accustomed to test. 

SOME SIMPLE, PRACTICAL TESTS FOR 
GLUE USERS 

To perform the tests described requires 
a degree of experience and an equipment 
beyond the reach of the ordinary buyer 
and user of glue. 

Certain tests may however be made 
that are of great value in determining 
important facts about the glue it is 
intended to buy and use. 

These tests could not be used as a basis 
for grading glue scientifically, but they 
are exceedingly valuable in determining 
its purity and its adaptability to the 
work in hand. 


33 





THE GLUE BOOK 


SAMPLING 

In the first place you should carefully 
sample your glue with a view to testing. 

Take several samples from various 
parts of the barrel. Flake glue is often 
made up of different varieties, and a 
single sample may not be at all represen¬ 
tative. Ground glue, from its very 
nature, is easily adulterated. It should 
be examined in a good light, for evidence 
of foreign substances. Examine flake 
glue carefully also for uniformity of odor 
and general appearance. If glue has been 
adulterated while in original form it is 
practically impossible to determine the 
adulteration by external appearance. 
Subsequent adulteration may be detected. 

BUBBLES 

If you should notice white bubbles, in 
the shape of round blots, on the surface 
of the glue, you have found evidence of 
decay. If there is any doubt in your 
mind you can complete the evidence by 

34 





THE GLUE BOOK 


moistening the glue. If it gives off a sour 
odor you have an additional indication 
of putrefaction. Such glue should be 
avoided. 

Bubbles may appear within the glue — 
not on the surface — without being an 
indication of putrefaction. As a matter 
of fact, bubbles are practically always 
found in certain high-grade glues, though 
practically never in low-grade bone or 
hide glues. They are supposed to be due 
to the air which gets in when the glue is 
poured into the moulds. When glue is 
originally dried on nets in very cool and 
dry weather, such bubbles are frequently 
found. Always beware of glue showing 
surface bubbles. 

SURFACE INDICATIONS 
Besides being free from bubbles or 
blots a good glue is smooth, though not 
necessarily glossy. Sometimes the very 
best glue will be of a dull color, and many 
inferior glues even have a very shiny sur- 

35 





THE GLUE BOOK 


face. The surface should be uniform in 
color and in appearance. 

COLOR INDICATIONS 

These are not important, as a rule. 
The color of any particular lot of glue 
should be nearly uniform; otherwise it is 
subject to the suspicion of adulteration. 

Bone glues are usually darker than 
hide glues, but some bone glues go 
through an artificial clarifying process 
which gives them the appearance of high- 
grade glues but really detracts from their 
strength. Very frequently oxide of zinc 
is added to glue, the effect being to make 
it set quickly, as well as to give it a light 
color. Some glues contain so much oxide 
of zinc that they are milk-white. Zinc 
oxide is not harmful except when added 
in very large quantities. 

ALKALINE OR ACID QUALITY 

The best glues are neutral as to acid 
and alkali. Glues with an excess of acid 

36 





THE GLUE BOOK 


should be avoided, especially when used 
with oak or chestnut or other woods with 
strong acid qualities, as the acids in the 
glue may unite with those in the wood 
in such way as to have a destructive 
effect upon the glue. In such cases the 
glue will granulate after a time and the 
work will pull apart. 

When a wood is being used that is 
strong in acid it is advisable to use a glue 
containing enough oxide of zinc to neu¬ 
tralize the acid in the wood. In making 
sizing for paper a glue containing either 
acid or alkali in excess should be avoided. 
It is also held by some authorities that 
acid in glue tends to bring about decay. 

To test for alkali or acid, dissolve a 
small quantity of glue in water and dip 
a piece of litmus paper into the solution. 
Acid will turn the paper violet or red. 
Alkali will turn it blue. Litmus paper 
may be procured at any drug store. 


37 





THE GLUE BOOK 


BREAKING QUALITY 

This is a simple test that affords an 
important indication of the quality of 
glue. Take a small piece between the 
thumb and forefinger of each hand and 
bend it. A very thin piece of good glue 
will bend without breaking. When it 
does break, if the edges are splintery, 
great tensile strength is indicated. A 
clean fracture, on the other hand, indi¬ 
cates a brittle, low-grade glue, which has 
been subjected to heat so long as to 
destroy the tissue; or else it has been 
made from bone stock. High-grade glues 
never show glassy fractures, but bone 
glues do. In making this test, the air con¬ 
ditions of the room should be taken into 
account. If the glue has been kept in a 
dry room it will naturally break much 
more readily than if it has been in a moist 
atmosphere. This is especially important 
to bear in mind if comparative tests are 
being made. 


38 





THE GLUE BOOK 


FOAM 

A simple test for foam is to beat a 
solution of glue with an ordinary egg- 
beater. Glue which shows foam, or in 
which foam does not quickly subside, 
probably contains impurities. Foam is 
especially frequent in alum-dried glues 
and in cheap bone glues. 

Some authorities believe that foam is 
caused by overheating, due to scalding 
by contact with steam jacket, or by steam 
coming into direct contact with the glue, 
or by heating for too long a time, or it 
may be due to the fact that all the grease 
has not been eradicated. 

Glue that foams at ordinary tempera¬ 
ture should be avoided for good work. 

GREASE 

A moderate amount of grease may be 
a good thing when using with clay or with 
colors, but a large proportion of grease 
should be avoided when making glazed 
or coated papers, or in general use. 

39 





THE GLUE BOOK 


A glue at ordinary temperature which 
is not over-heated on which a scum rises 
has an excessive amount of grease. It 
shows that the glue has not been properly 
skimmed in manufacture. 

KEEPING PROPERTIES 

The keeping property of glue may be 
determined by letting the glue-jelly stand 
for several days exposed to the air, and 
noting any deterioration. It is customary 
to let the jelly stand at room temperature 
— but if the glue is to be kept under any 
special conditions the test should be 
made as nearly under these conditions 
as possible. 

ODOR 

Deterioration is always accompanied 
by a sour odor. Avoid using any glue 
that does not smell clean and sweet. 

LABORATORY TESTS 

Up-to-date practice in all the larger 
concerns using glue demands a laboratory 
for making tests. An expert is put in 

40 





THE GLUE BOOK 


charge and the glue analyzed chemically 
as well as for its physical properties. This 
method cuts the guess-work down to a 
minimum. Manufacturers whose output 
would not permit the employment of an 
expert all the year round can have glue 
analyzed in laboratories maintained for 
such purposes. It means often a great 
saving of money in the end to learn the 
exact properties of the glue you propose 
to use, or that you may be actually using. 

We may also repeat what we have 
already said about securing competent 
advice from manufacturers. The glue 
user who takes a responsible manufac¬ 
turer or glue house into his confidence 
will secure valuable counsel. 

It is to the glue maker's and glue sales¬ 
man's interest to have you secure good 
results. They have a large experience 
to draw on, and when checked up by the 
results from actual practice in your glue 
room their advice in regard to the selec¬ 
tion of glues is usually worth heeding. 

41 












CHAPTER IV 

CORRECT METHODS IN GLUE-ROOM 


I T is quite certain that glue-room 
methods in many factories are years 
behind the times. This is due to 
poor equipment, to ignorance and to 
carelessness. Many factories could not 
continue in business if the hit-and-miss 
methods of the glue-room prevailed in 
other departments. 

It is possible to spoil the very best glue 
by improper methods of preparation; 
and not only is a vast amount of glue 
rendered totally unfit for satisfactory 
work, but a great deal is wasted; the 
total loss, through faulty methods, being 
about 25% of the entire amount used. 

There is no reason why there should be 
such loss in the glue-room. The proper 
methods of procedure have been definitely 
established. Putting them into effect 
not only saves glue, but it enables better 
work; saves time of workmen, and 
increases greatly the general efficiency 

43 






THE GLUE BOOK 


of glue-room operations. The following 
rules are a guide to correct practice. 

ALWAYS SOAK GLUE IN COLD WATER 
BEFORE MELTING 

The function of soaking is to get back 
into the glue the liquid it originally 
contained. 

Soaking in cold water gets the glue 
into proper condition to dissolve readily 
when heat is applied. If glue is soaked 
in warm water, or if melted without 
soaking, the glue on the outside will dis¬ 
solve at once, and this will coat the 
remainder with a film, so that it will not 
readily dissolve, except when heat is 
applied in a degree that is harmful. 

Glue has an affinity for cold water. 
Good glue will absorb from l l /2 times to 
2j/2 times its weight of cold water. 

If glue is in flakes or strips, break up 
into small pieces. Soak the pieces from 
10 to 12 hours in cold water. Soak ground 
glue 1 to 4 hours in cold water. Naturally 

44 





THE GLUE BOOK 


the thinner the glue the less time required 
for thorough soaking. The glue should 
be soaked through thoroughly and not 
merely moistened on the outside. You 
can determine whether the soaking has 
been completed by breaking a piece in 
two and noting conditions at the cen¬ 
tre. If pieces are permitted to stick 
out beyond the level of the water, the 
natural result is that such pieces will be 
only partially softened. As the melting 
proceeds, these will slip to the bottom 
of the kettle, and in order to melt them 
long heating and high temperature are 
required. This means damaging the 
strength and adhesiveness of the glue. 

In soaking ground glue it is a good 
plan to keep stirring as the glue is added 
to the water in the soaking vessel, as this 
helps to keep the fine particles of glue 
immersed in the water, instead of float¬ 
ing on the top. This is true also of thin- 
cut, high-test glues. 


45 





THE GLUE BOOK 


USE ONLY PURE, COLD WATER 
In soaking and thinning glue, use only 
pure, cold water. Unless heater is pro¬ 
vided with pure water attachment or 
pure water chamber, avoid using water 
from the glue heater. Do not use water 
from boilers, for such water contains 
pipe-rust, acids from boiler compounds, 
sediment, and other matter extremely 
harmful to glue. See to it that all soak¬ 
ing vessels are scrupulously clean. 

TESTING GLUE BY WATER ABSORPTION 
The soaking of glue in cold water 
before using is employed in some factories 
as a basis for comparative test of working 
quality. The amount of water absorbed 
may vary as much as 10 ounces in half 
a pound. Other things being equal, the 
glue that absorbs the most water is of 
course the cheapest to use. As a com¬ 
parative test, melt up say 10 pounds of 
glue and see how much work it will do 
compared with the glue you are now using. 

46 





THE GLUE BOOK 


A SIMPLE GLUE TESTER FOR DETERMINING 
WATER ABSORPTION 

A simple and accurate apparatus may 
be had for determining the amount of 
water the glue will absorb for best work¬ 
ing results, and also whether the amount 
of water actually used is the proper 
amount for this particular glue. 

It is important to know these facts, 
since the more water a glue will absorb 
under proper working conditions, the 
cheaper that glue is to use. 

The apparatus in question is illustrated 
on the next page. It consists of a copper 
pot and a hydrometer arranged for a 
temperature of 75° C., or 167° F. A 
sample of the glue to be tested is poured 
into the pot and the hydrometer is 
slowly allowed to sink into the solution 
until it finds its correct position. If the 
glue solution is, for instance, 1 part glue 
to 3 parts water, the hydrometer will 
drop to 25 on the hydrometer scale. 
This will show that you have 25% dry 

47 





THE GLUE BOOK 


glue in the solution. The hydrometer is 
fitted with a temperature correction scale 
that enables the readings to be adjusted 
to the temperature of the glue solution. 

By noting the working 
qualities of glue prepared 
with various proportions 
of water, you can deter¬ 
mine what is the correct 
amount of water to use, 
and then by using the hy¬ 
drometer as each batch is 
prepared, you can be sure 
that the correct proportions 
are always being used. By 
making readings from time 
to time with the hydrom¬ 
eter, you can also deter¬ 
mine the amount of evapo¬ 
ration that is going on, and 
in this way guard against 
the glue becoming too thick 



for proper use. 


48 





























THE GLUE BOOK 


No special skill is required to use the 
hydrometer, and the readings are so 
quickly made, that tests can be made in 
every department in which glue is used 
without loss of time. 

MELTING, OR DISSOLVING, GLUE 
After the glue has been soaked in the 
manner described, the most important 
part of the process is undertaken — that 
is, the melting of the glue by application 
of heat. 

The words “most important” are used 
advisedly. It is safe to say that most 
of the damage done to glue occurs in 
the melting process. There are all kinds 
of ways of melting glue, but many of 
them absolutely ruin glue for practical 
work. As this is a very important sub¬ 
ject, it is well to get the rudiments thor¬ 
oughly in mind —and for this purpose 
the reader should remember what has 
been said about the nature of glue — that 
it is made from animal matter; and that 

49 





THE GLUE BOOK 


it is composed of innumerable small 
fibres on whose strength the holding 
power of the glue depends. 

Whatever injures and breaks down 
these fibres inevitably weakens the glue; 
so that in melting, every care must be 
observed to avoid the breaking down 
of the glue fibres. 

The most common destructive agent is 
heat. Just as the application of heat 
breaks down the fibres of a roast of beef, 
rendering it “tender” as the saying is, 
so the prolonged application of heat, or 
heat of too great an intensity, will 
destroy the glue-fibres, and therefore 
radically impair their value for actual use. 

So, it is absolutely necessary to employ 
no more heat in melting glue than is 
required to reduce the soaked mass to 
the proper working consistency. 

DO NOT HEAT GLUE HIGHER THAN 150° F. 

By actual experience it has been deter¬ 
mined that a temperature of 130° to 

50 





THE GLUE BOOK 


150° F. is all that is required to melt the 
glue to the requisite consistency; any 
greater heat is actually harmful, as it 
assists just so much more in the process 
of disintegration. 

The term “boiling,” or “cooking,” never 
should be applied to the process of glue 
melting. These words imply a tempera¬ 
ture of 212° F. — and such a temperature 
is ruinous to glue. In producing glue 
from the original stock — from the hides, 
bones, sinews, etc., — boiling is necessary, 
in order to extract the gelatinous matter 
— but as we have already seen, the 
longer the stock is boiled, the weaker 
the product. “First boilings” are always 
best. In preparing for use, however, 
boiling is not necessary; therefore, never 
heat glue above 150° F. 

APPLY HEAT INDIRECTLY 

Heat never should be applied directly, 
as this results in burning, or scalding, 
the glue. 


51 





THE GLUE BOOK 


Some glue melting appliances have 
been constructed in which steam is 
turned directly upon the glue mass. This 
is bad practice of the most harmful kind. 

Steam never should come into direct 
contact with glue. The temperature of 
steam is always at least 212° F. — under 
pressure it is much higher — and conse¬ 
quently it cooks the glue and destroys 
the fibres. Live steam burns glue just 
as it burns your hand if turned directly 
upon it. 

The destructive effect of live steam 
upon glue may not be noticed at once, 
but work on which overheated glue has 
been used will eventually pull apart on 
account of the destruction of the glue 
fibres. 

LIVE STEAM RUINS GLUE 

One of the largest glue manufacturers 
in the country makes the following com¬ 
ment on this subject: 

“In regard to the effect of live steam 
turned into a pot of glue, whether flake, 

52 




THE GLUE BOOK 


ground, or jelly — the glue would become 
overheated, and you know that always 
has a disastrous effect. The tempera¬ 
ture of live steam is 212°, and under 
pressure it is even higher, so that at least 
the glue around the pipe will attain a 
temperature of 212°. The effect will be 
that the glue will be cooked to death and 
lose its strength. We would certainly 
discourage the application of live steam 
for dissolving glue as there is nothing 
to gain by it and everything to lose.” 

Opinions of other manufacturers are 
unanimous on this point. 

“We know of factories where they have 
made a careful test,” writes one, “and 
the results obtained from glue where it 
was melted with a live steam jet and 
where it was dissolved in a jacketed 
kettle were so greatly in favor of the 
latter method that it is used universally 
today.” 

A further vital objection to the use 
of steam direct is that the steam contains 


53 




THE GLUE BOOK 


acids from boiler compounds, dirt, pipe- 
rust and sediment, all of them injurious 
to the strength and to the elasticity of 
glue. 

Then too, glue always takes up mois¬ 
ture from steam. This changes the con¬ 
sistency of the glue. It leads to guess¬ 
work. The quantity of water added to 
glue must always be exactly regulated. 
Turning live steam on glue prevents pro¬ 
portions of glue and water remaining 
constant. 


USE A THERMOMETER 

The only safe procedure in melting 
glue is to use a thermometer. If glue 
is melted in an open pot, or one in which 
the contents of the glue chamber can be 
reached easily, an ordinary drop ther¬ 
mometer, encased in a frame for protec¬ 
tion, may be used. 

It is preferable, however, to have the 
thermometer a part of the apparatus, 
with the mercury tube extending into 

54 





THE GLUE BOOK 


the glue chamber. In this way it is 
easy to keep watch on the temperature 
of the glue mass at all times. 

An improvement even on this method 
is found in the automatic temperature 
controller that may be had with some 
glue melting appliances, by which the 
supply of heat is automatically regulated. 
When the temperature in the glue cham¬ 
ber passes 150° F. — the absolute maxi¬ 
mum of safe temperature — the valve 
automatically closes and shuts off the 
heat, re-opening again when the temper¬ 
ature has lowered from 5° to 10°. By the 
use of the automatic temperature con¬ 
troller the temperature is kept at the 
proper point, and there is no necessity of 
making observations with the thermom¬ 
eter except to verify your controller. 

The temperature controller not only 
permits the scientifically correct prepara¬ 
tion of glue, preventing overheating and 
ruined work, but saves also in expense 
of supervision. 


55 




THE GLUE BOOK 


HEAT GLUE SLOWLY 

Glue should be heated slowly, requiring 
about 30 minutes. Rapid heating dis¬ 
solves the outer portions of the glue 
quickly, and a scum is then formed over 
the rest of the glue, preventing its proper 
melting. 

The following precautions will be found 
useful to put into practice. 

CLEANING THE MELTING POT 

Dirt enters the melting pot through 
the glue itself, the introduction of dirty 
brushes, or the exposure of the pot to 
dust, etc. If glue is melted in a dirty 
pot, the skin forming on the surface of the 
glue liquor gradually accumulates at the 
sides of the kettle and slowly decomposes. 
This may or may not fall into subsequent 
melts, thus contaminating them. The 
only way to make sure that it will not 
do so is to clean the pot. 

Much unnecessary waste of glue may 
be avoided through observance of the 

56 





THE GLUE BOOK 


following procedure. The contents of 
the melting-pot exhausted, scraps of 
dried glue, as well as scraps of partially 
dried jelly adhering to the sides should 
be detached mechanically, as thoroughly 
as possible, and examined. If clean, 
they may be replaced in the bottom of 
the kettle; if dirty, they are to be set 
aside temporarily. 

In the first instance, they are covered 
with the minimum of water necessary 
to soften, and the sides of the kettle 
swabbed with a little water in order to 
soften any glue that has dried and has 
not been detached mechanically. The 
pot is then gently heated in order to 
bring the scraps into solution, this solu¬ 
tion used in work, and the pot thoroughly 
washed out with hot water and cooled 
before soaking a fresh portion of glue. 

If the scraps have proved dirty, but 
not sour, they may be kept warm enough 
to permit the dirt to settle, when the 
glue may be used without risk. If sour 

57 





THE GLUE BOOK 


they must be thrown away. If the glue 
pot is properly cleaned there is no danger 
of souring and all the glue may be used 
without waste. 

It may be contended that much labor 
may be saved by adding sufficient water 
for the next melt, and through this means 
soften all glue adhering to the kettle in 
connection with that added fresh. It 
will be found, however, that the freshly 
added glue will absorb the bulk if not all 
of the water, leaving adhering scraps 
practically unsoftened, which in this way 
continue to accumulate, interfering with 
the proper working of the glue. 

Pots, kettles, brushes, everything that 
comes into contact with glue, should be 
regularly and rigidly inspected, and kept 
absolutely free from dust and dirt. This 
is extremely important. 

USE COPPER AND BRASS OR ALUMINUM 
UTENSILS 

An important aid to cleanliness is the 
use of copper, aluminum or brass for all 

58 





THE GLUE BOOK 


parts of the apparatus with which glue 
comes into contact. Not only are copper, 
aluminum and brass the cheapest mater¬ 
ials to use in the long run, due to their 
resisting acids in glue, water and steam 
which quickly corrode iron, but copper, 
aluminum and brass are practically self¬ 
cleaning. 

Iron equipment is especially bad. It 
is most expensive in the end, for iron is 
quickly eaten away by acids in glue and 
water. Iron rusts, and the rust impairs 
the color and quality of the glue liquid. 
Do not use iron vessels under any condi¬ 
tions. 

GUARD AGAINST EVAPORATION 

A great deal of waste in the use of glue 
is due to evaporation. If glue is heated 
in open pots, evaporation is very great. 
Evaporation weakens glue; makes it too 
thick for use, and also makes it very 
uneven in quality. Glue should always 
be melted in a closed vessel. 


59 





THE GLUE BOOK 


DO NOT MELT TOO MUCH AT 
ONE TIME 

As glue deteriorates quickly if allowed 
to stand, no more should be prepared 
than is needed for a single day's work. 
It is even better to prepare it twice or 
oftener during the day. 

If glue is dissolved at the proper tem¬ 
perature and kept at that same tempera¬ 
ture after melting, no noticeable deterior¬ 
ation results during the course of the 
working day. But if allowed to stand 
over night its value decreases, and it 
should not be mixed with fresh glue, as 
it is not of the same consistency. 

With practice and observation you 
can easily determine each day's needs in 
advance and prepare each morning just 
the right amount. 

CLEANLINESS OF FIRST IMPORTANCE 

Glue is extremely sensitive to impuri¬ 
ties. 


60 





THE GLUE BOOK 


Cultures of germs are grown by bacteri¬ 
ologists in gelatine glue because they 
afford an ideal breeding place for germs. 

Glue quickly absorbs odors, and decays 
rapidly if exposed to impurities. 

Decayed or decaying glue is not only 
extremely unpleasant to handle, but it is 
worthless to work with. Keep your glue 
clean. Keep it away from strong odors. 
Glue will keep sweet and clean before 
melting just as long as you care to keep 
it so. 


KEEP GLUE-ROOM WARM AND 
FREE FROM DRAFTS 

Glue can not be expected to do good 
work if not kept at uniform temperature. 
See that the glue-room is of a temperature 
that facilitates uniform consistency of 
glue. Avoid possibility of drafts and 
consequent chilling of the melted glue. 

Do not let glue freeze. If glue-jelly is 
frozen through it will crumble and act 
about like overheated glue. Glue frozen 
61 





THE GLUE BOOK 


only around the edges does not show 
pronounced deterioration. Do not take 
any chances. Keep the glue-room tem¬ 
perature above freezing at all times. 

USE BY WEIGHT 

Glue is sold by the pound and should 
be used by the pound. Weigh not only 
the glue, but weigh the water as well. 
Keep an accurate record of weights. 

STORING 

Glue should be stored in a dry place. 
Barrels should not be unheaded prema¬ 
turely, and after having been opened 
should be kept covered when not in use. 

APPLYING GLUE 

All surfaces to which glue is to be 
applied should be warm and dry. Hot 
glue will chill if applied to a cold surface, 
and if wood is being glued, moisture will 
have the effect of clogging the pores of 
the wood. Heat dries and expands the 
pores, allowing the glue fibres to pene- 
62 





THE GLUE BOOK 


trate deeply, thus insuring perfect 
adhesion. 

At the same time there is danger of 
getting wood too dry, making it absorb 
too much glue, and too speedily. This 
causes a very quick setting, and may 
result in “starving” the glue joint. 

Some users on this account recommend 
adding a little moisture to the surface of 
stock, by steaming or by application of 
a little warm water. There is more or 
less uncertainty on this subject. As a 
general conclusion it is safe to say that 
stock must always be warm; surplus 
moisture must be expelled; no “green” 
stock must be used. 

Here again, as in so many other prob¬ 
lems of the glue-room, observation of 
results under actual conditions should 
be the guide to practice. 

SECURING WORKERS* CO-OPERATION 

One more thing of extreme importance 
— the employer should do everything 


63 





THE GLUE BOOK 


possible to secure the co-operation of 
every worker in the glue-room, from the 
foreman down, in using proper methods. 
A little personal interest here will be 
rewarded a thousand fold. Provide your 
workmen with proper equipment, which 
in itself encourages cleanliness, and show 
them how the quality of work may be 
improved. 

Show them that an unclean, ill-smelling 
glue pot is unnecessary. Show them 
that there is a right way, and a wrong 
way, to prepare glue — and the right 
way is the way to use. Introduce system 
into the glue-room, as into every other 
part of the plant. 

Many workers are still ignorant of 
modern glue methods. It is the duty 
of the employer to know what the correct 
practice is, and to see that it is employed 
in his glue-room. 


64 





CHAPTER V 

MODERN GLUE-ROOM EQUIPMENT 

W ITH the increased knowledge 
of the nature of glue, and of 
proper methods of handling, 
has come a great improvement 
in apparatus used. The primitive way of 
melting glue was to heat it in an open 
pot over a fire. No heed was given to 
the loss through evaporation; nor to the 
scalding of glue; nor to the dirty con¬ 
dition of the glue-pot, and consequently 
contamination of fresh glue by the remains 
of former melts frequently occurred. 

We say “primitive” methods advisedly 
in speaking of this old-time way of melt¬ 
ing glue; for in the light of modern knowl¬ 
edge such methods belong to a day gone 
by. Yet some glue-rooms still use the 
old open glue-pot, and many others use 
apparatus which shows little, if any, 
improvement. 

Modern glue-room appliances are now 
available for every glue-room, for every 

65 






THE GLUE BOOK 


purpose. No glue user, large or small, 
can afford to use any but modern, scien¬ 
tific equipment. The saving in time, 
and in materials, and in improved quality 
of the completed work, and in the greater 
respect and increased efficiency of workers 
in the glue-room, all these things result 
in quickly repaying the increased outlay 
required. 

ONLY COPPER, BRASS, ALUMINUM SHOULD 
COME INTO CONTACT WITH GLUE 

The advantage of using copper, brass, 
and aluminum in glue-room appliances, 
due to their self-cleansing properties, 
already has been mentioned. 

In apparatus designed for melting glue 
the use of copper, brass, and aluminum 
is absolutely required for economy and 
good results. Copper, brass, and alumi¬ 
num are the only materials available 
that are not affected unfavorably by the 
action of acids in glue, steam and water; 
by boiler compounds, dirt, pipe-rust and 
sediment. 


66 





THE GLUE BOOK 


An iron agitator or stirrer in a glue 
heater is corroded so quickly by the acids 
in glue, water and steam that in six 
months it is unfit for use. 

A brass agitator, on the other hand, 
will last practically forever. So it is with 
every part of the glue heater with which 
glue comes into direct contact. 

The glue user who has had experience 
with galvanized iron heaters does not 
need to be told that the iron quickly is 
eaten away and the apparatus rendered 
unfit for use. It is certainly the part 
of wisdom to invest in copper, brass, and 
aluminum equipment, to which metals 
there is practically no “wear-out.” 

Glue-room equipment of iron is still 
sold, but only because there are still 
some users who are so blinded by the 
initial small saving in outlay, as not to 
see the saving that accrues in the end 
from using indestructible materials — 
and the additional saving due to good 
work and economy of glue. 

67 




THE GLUE BOOK 


A SCIENTIFIC GLUE-HEATER 

The facts already mentioned about 
the melting of glue should be borne in 
mind in choosing a glue melter, or glue- 
heater— always remembering in partic¬ 
ular that it is of utmost importance that 
the heating agent should not come into 
direct contact with glue, and that the 
glue should not be overheated in prepara¬ 
tion. 

The glue-heater that has been proved 
most economical and efficient in wide¬ 
spread use has an air-tight glue chamber 
(to prevent evaporation), surrounded by 
a water-jacket (to prevent burning or 
scalding glue), the water in the jacket 
being heated either by direct injection 
of steam or by the use of copper heating 
coils. Electricity is also used success¬ 
fully as a heating agent. 

The heater is made of copper and brass 
throughout, and is therefore not affected 
by the harmful effect of acids in glue, 
steam and water, dirt, grease, pipe-rust, 
68 





THE GLUE BOOK 


sediment and other harmful substances. 
In this heater glue is reduced to a uni¬ 
form and correct working consistency, 
and with unusual speed, if desired; 5 
gallons of glue may be melted in less than 
15 minutes, and as much as 50 gallons in 
less than one hour. 

It has already been noticed that exces¬ 
sive speed in heating requires a degree 
of heat that is injurious. 

A thermometer is provided with this 
heater that gives accurate readings of 
the temperature within the glue chamber, 
so that the heat may be turned off when 
the danger point of 150° F. is reached. 

THE AUTOMATIC TEMPERATURE 
CONTROLLER 

A still more recent and valuable 
improvement is the automatic tempera¬ 
ture controller, a thermostatic valve 
which operates automatically to keep 
the temperature in the glue chamber 
between 145° F. and 150° F., or at any 
temperature for which it is set. 

69 





THE GLUE BOOK 


Not only overheating of the glue is 
prevented, but expense of supervision 
is reduced. The heater does not need 
to be constantly watched for fear glue 
will not be kept at correct temperature. 

This particular heater is also provided 
with a brass agitator (hand or power) for 
keeping glue thoroughly mixed while 
melting, and with a special faucet by 
means of which the melted glue is drawn 
off without dripping or clogging. It is 
made in sizes from 2 gallons to 500 gallons 
liquid capacity, and for use with any 
heating agent — gas, electricity, or steam. 

An apparatus of this kind not only 
facilitates economical melting of glue, 
by preventing evaporation, waste, for¬ 
mation of scum, sour and dirty glue, but 
it also insures uniform “spread.” Fur¬ 
thermore, it is a great incentive to accur¬ 
acy and cleanliness on the part of work¬ 
men, encouraging them to good work 
by providing them with a neat and clean 
glue melting appliance, in contrast with 

70 





THE GLUE BOOK 


the old-fashioned, unsightly and ill-smell¬ 
ing “‘glue-pot;” and providing them also 
with glue that has been properly prepared. 

KEEP STEAM AWAY FROM GLUE 

Above all, keep steam away from glue. 
Some glue-melting devices are on the 
market in which glue is prepared by sub¬ 
jecting to the direct application of steam. 
This produces only bad results. All 
authorities are now agreed on this subject. 
It is safe to say that the chief develop¬ 
ment in glue-room methods of the past 
ten years hinges entirely on the discovery 
of these facts: that steam ruins glue; 
that glue never should be heated above 
130° to 150° F. at the utmost; that the 
other properties in steam — boiler com¬ 
pounds, acids, dirt, pipe-rust, sediment, 
and grease — are absolutely injurious to 
glue. 

Do not let the argument of speed blind 
you to the damage resulting from the 
live steam type of dissolver. If you 
want speed, use a type of instantaneous 

71 





THE GLUE BOOK 


dissolver that prevents steam from com¬ 
ing directly into contact with glue. The 
very best practice, the one generally 
recommended by experts, is to heat glue 
slowly, with a heat not above 130° to 150° 
F. Then the glue is in the very best 
possible condition for work. 

The effect of acids is such that they 
have been known to turn a pot of good 
glue black. 


GLUE SPREADERS 

In wood-working establishments where 
much glue is used, it should be applied 
mechanically, by means of glue spreaders. 

Some spreaders are made with Brussels 
carpet covering for rolls, but this is not 
good practice. The carpet covering 
absorbs dirt quickly, is difficult to keep 
clean, is liable to tear, is sure to stretch 
and eventually rots and wears out. 

The simplest, cleanest, and cheapest 
method in the long run is to have rolls 
with corrugated surface; even spread is 

72 





THE GLUE BOOK 


thus assured, and there is practically 
no “wear-out” to them. 

In order to keep glue at right temper¬ 
ature during use, it is best to have the 
glue-pans surrounded by heating coils. 
These may easily be connected with the 
steam boiler or gas heater; or electricity 
may be used. 

A further improvement is to have the 
spreader connected with the glue heater, as 
then only a minimum quantity of glue need 
be carried in the pans. By this method 
a quantity of glue sufficient for a day's 
work or half-day's work may be melted 
in the morning and maintained steadily 
at uniform thickness and temperature 
until used. The melted glue is fed to 
the pans only as needed, through open 
copper troughs. 

Glue pans should of course be made 
of copper, for the reasons already men¬ 
tioned. Another advantage is that copper 
pans are self-cleaning, as glue does not 
adhere to this material. 

73 





THE GLUE BOOK 


Spreaders may be had as a single-roll 
machine, for coating one side of stock, 
or as a double-roll, for coating both sides, 
or as a combination single and double¬ 
roll. They may be operated by hand 
or with power. When used with power 
a good operator can coat 13,500 lineal 
feet per day, with a good machine. The 
results with a glue spreader are largely 
due to the proper adjustment of the 
scrapers. 

Glue spreaders can be used to coat flats, 
edges, straights and mitres equally well. 

For coating plain and straight surfaces, 
use a solid roll. For tongued and grooved 
pieces, V-shaped stock, dovetails and 
other irregular shapes, use a brush roll. 
Some spreaders are fitted with combina¬ 
tion solid and brush roll; a very conve¬ 
nient and economical arrangement. 

The spreaders should be kept scrupu¬ 
lously clean, and also the brushes, if any 
are used. Clean brushes by filling glue 
pan with hot water and revolving the 

74 





THE GLUE BOOK 


brush in it until all the glue has been 
removed. 

CLAMPS AND PRESSES 

After gluing, the work should be kept 
under pressure for a sufficient length of 
time to insure perfect adhesion. In the 
case of hide glues the time required is 
from three to four hours. The time 
varies with variations in the glue, in con¬ 
dition of stock, and in temperature of 
room. No general statement can be 
made to cover the case; experience is 
the best guide. Either retaining clamps 
or presses are used. 

Pressure should be distributed as 
evenly as possible. Presses may be had 
in almost every style for every need — 
open on one side, or on two sides; for 
veneered stock; sectional presses; etc. 
Very excellent presses are being made 
of structural steel. They are practically 
indestructible, very efficient, and yet 
simple in operation. 


75 




THE GLUE BOOK 


In selecting a veneer press equipment 
the amount of pressure per square inch 
must first be determined. Opinion varies 
with different manufacturers, some using 
100 pounds, some 200 pounds, per square 
inch. The best general results are ob¬ 
tained by using 150 pounds per square 
inch. All presses made with a 2-inch screw 
should be designed to withstand a pressure 
of 8 tons or 16,000 pounds per screw. 
To find the tonnage of press that you 
require, multiply the length by the width 
of stock, this by the pressure per inch 
you desire and divide the results by 2,000. 
This will equal the tons pressure required. 
The number of screws per press can then 
be determined. 

DISTRIBUTING GLUE IN LARGE PLANTS 

Glue is used in the wood-working 
industry mainly for making joints and 
veneers. 

In large establishments, where many 
workmen are employed, a good plan for 

76 





THE GLUE BOOK 


distributing the melted glue is to arrange 
a battery of small glue pots, or warmers, 
strung along a pipe line running from 
the steam boiler or gas heater. 

Individual pots of copper which are 
filled at the central source of supply fit 
into cast-iron jackets, kept warm by 
steam which comes from the pipe line. 
The requisite temperature is thus main¬ 
tained at minimum cost. 

The valves may be so arranged as to 
cut off any warmer not in use, avoiding 
waste of heat. The arrangement is very 
satisfactory even in comparatively small 
establishments, and may be adapted to 
any number of individual pots. 

ADVANTAGES OF ELECTRICAL EQUIPMENT 

When steam is used as the heating 
agent, only about one-fifth the amount 
of heat generated is actually used for 
heating the glue. Four-fifths of it radi¬ 
ates through the pipes and creates a heat 
so intense that the efficiency of the work- 
77 





THE GLUE BOOK 


men is reduced fully one-half in summer. 
With gas as the heating agent, the same 
conditions are present as with steam, plus 
the fire risk, which in itself is so great as 
to make gas extremely inadvisable. 

Electricity is coming into greater favor 
every year, with the improvement of 
electrical glue-heating appliances. Elec¬ 
tricity is still too expensive to justify its 
use as a heating agent, except for the 
exact purpose desired, but modern electri¬ 
cal devices, including the jacketed, heat- 
retaining glue pot, make it possible to 
use electricity without waste. 

The cost is less than either steam or 
gas and its advantages are so great that 
thousands of institutions are now using 
these “fireless” glue heaters. The best 
electric glue heaters are made of copper 
and brass, the greatest conductors of 
heat. They require much less heat than 
any other pot and the heat is required 
for just about one-fifth the time, owing to 
the heat-retaining jacket. 

78 





CHAPTER VI 

WHICH GLUE TO USE 

T HE answer to this question depends 
so largely on the individual con¬ 
ditions, that only very general 
suggestions may be given. We 
have already suggested the need of 
experimenting and accurately record¬ 
ing the results of using various kinds of 
glue. Once again, your dealer will give 
you good advice nine times out of ten — 
and your own experience should afford 
the most valuable check on his sugges¬ 
tions. 

In general, the following glues are 
indicated: 

Wood joints — High test hide glues. 
They make strong, firm joints, which is 
extremely important, as joints are subject 
to more or less tension; and they set 
rapidly. 

Veneers — A moderately high test mix¬ 
ture of bone and sinew or bone and hide. 
The higher test glues set too quickly 

79 







THE GLUE BOOK 


for this particular kind of work. If a 
spreading machine is used, avoid a glue 
that tends to foam. Sometimes foaming 
is caused by its spreading too fast. Over¬ 
heating glue also tends to foam it. This 
can be overcome by the addition of sweet 
oil or vaseline, paraffine or wax candle, 
but it is objectionable when veneering. It 
is best to be sure you have a glue that 
will not foam. Your dealer can tell you 
what glue to use. 

Sizing — Use a glue free from grease 
and foam and one that flows freely. 

Paper Boxes — A quick-setting hide 
glue is indicated for setting-up. For 
covering, a lower test bone glue is pre¬ 
ferred, as it does not set so quickly. 
Paper box manufacturers are troubled 
more or less with foaming glue and can 
use the remedy suggested in the para¬ 
graph on veneers, as this will not be 
objectionable in paper box work. 

Belting and Other Leather Goods — 
Here the principal requirements are 
80 





THE GLUE BOOK 


flexibility, resistance to moisture and 
tenacity. The higher test glues are 
generally preferred. 

Bookbinding — For pasting covers, a 
low-grade bone glue answers all require¬ 
ments sufficiently well. For rounding 
and backing, where strain is exerted, a 
high-grade hide glue should be used. 

For Emery Purposes — Very high- 
grade glue that has been carefully pre¬ 
pared to eliminate all acids, alkalies and 
impurities. A good emery glue possesses 
superior water-absorbing qualities. To 
test a glue for emery purposes, soak an 
ounce in about five times its weight of 
water at room temperature for 48 hours. 
If at the end of the time the water shows 
discoloration, or if decomposition is evi¬ 
denced by a disagreeable odor, the glue 
is not adapted to emery use; otherwise 
it may safely be used. Weigh glue after 
the operation, to get an idea of its water¬ 
taking properties. 


81 




THE GLUE BOOK 


HOW MUCH TO PAY FOR GLUE 

While the high test glues cost more per 
pound, they go farther and do better 
work, except in cases when their quick¬ 
setting characteristics are an objection. 

How much you can afford to pay for 
your glue is a question that you must 
answer from your own observation and 
tabulation of results. In certain lines it 
would be foolish to use a high-grade glue, 
where the work would not benefit in pro¬ 
portion to the increased expenditure. 
Any attention given to the subject will 
be well repaid. 

KEEP ACCURATE RECORDS 

Always keep accurate records, and 
base your future purchases upon the 
demonstrated comparative results already 
attained by the various glues you have 
used in actual practice. 

No glue is good to use unless properly 
prepared. A 16-cent glue may be reduced 
to the grade of an 8-cent glue by over- 
82 





THE GLUE BOOK 


heating. The grade of the glue at the 
time it is used is the important thing. 

Do not by faulty methods of prepara¬ 
tion impair the working quality of your 
glue. A glue of moderate high grade 
properly prepared is better for practical 
purposes than a high-grade glue whose 
working quality has been destroyed by 
excessive or prolonged heating. 

WATERPROOF GLUE 

Sometimes it is desired to use glue with 
waterproof qualities. Glue is rendered 
practically waterproof by adding a small 
quantity (about 1%) of ammonium or 
potassium bichromate to the glue liquid. 
Upon hardening, the glue then becomes 
waterproof. Adding a small quantity of 
formaldehyde to the liquid glue will help 
it to resist the action of water after it has 
dried for some time. 

Others suggest dissolving glue in an 
equal quantity of water and adding about 
as much linseed oil as water, with the 

83 





THE GLUE BOOK 


aid of heat, until a jelly is formed. This 
mixture is said to be practically water¬ 
proof. 

A patented process has recently been 
put out for which the claim is made that 
it can be applied to any glue irrespective 
of grade or make, rendering it absolutely 
waterproof. The result is attained by 
mixing the glue with certain chemicals 
in specified proportions, and then adding 
a certain amount of formaldehyde. Any 
amount of glue can be treated and the 
process is said to be most effective. 

VEGETABLE GLUE 

Of recent years efforts have been made 
to find a substitute for animal glue. The 
effort has met with success to a certain 
extent for particular kinds of work. Prob¬ 
ably the newest addition to the list of 
vegetable glues is the mineral glue-silicate 
of soda. Liquid silicates were first sold 
for the manufacture of soap. In recent 
years certain forms have been used for 

84 





THE GLUE BOOK 


light adhesive paper work. It is used in 
places where glue is too slow setting. 

QUICK SETTING GLUES 
When a glue is desired to set very 
quickly the manufacturer can usually 
furnish glue with the setting qualities 
desired for the particular work in hand. 
If this cannot be done, for any reason, 
remember that the temperature of the 
glue is an important factor. A low tem¬ 
perature aids in quick setting. Some 
paper-box manufacturers have had suc¬ 
cessful results in quick setting by adding 
a small quantity of turpentine to the 
liquid glue. Some add silicate of soda. 

FLEXIBLE GLUES 

Specially made glues are supplied by 
manufacturers for work in which flexi¬ 
bility is needed. An easy way to increase 
the flexible quality of glue is to add a 
little glycerine to the liquid glue. 


85 





SEP 19 1913 


The Republican Publishing Co., Hamilton, Ohio 


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